Video ASIC
The video processor accepts either RGB
or YUV (NTSC/PAL) input. A video
buffer is provided to allow artifact-free
scan conversion of input video. Gamma
correction and colorspace conversion
are applied to enable accurate mapping
of input colors to the wide laser color
gamut. A scaling engine is available
for upconverting lower-resolution
video content.
A proprietary virtual pixel synthesis
(VPS) engine uses a high-resolution
interpolation to map the input pixels to
the sinusoidal horizontal trajectory. The
VPS engine demonstrates how projector
functions have been shifted from the
optics to the electronics in the scanned
laser paradigm. It effectively maps the
input pixels onto a high-resolution
virtual coordinate grid. Besides enabling
the repositioning of video information
with subpixel accuracy onto the sinusoidal scan, the VPS engine optimizes the
image quality. Brightness uniformity is
These super-small,
low-power projector
systems will open up
the display bottleneck
for mobile devices,
allowing information
to be accessed and
shared more easily from
portable devices.
managed in the VPS engine by adjusting coefficients that control the overall
brightness map for the display.
Optical distortions—including keystone, parallelogram, and some types of
pincushion distortion—can be compensated by using the VPS engine to adjust
the pixel positions. The VPS engine
also allows the pixel positions for each
color to be adjusted independently. This
simplifies the manufacturing alignment
of the IPM by relaxing the requirement
that the three laser beams be perfectly
aligned. The positions of the red, green
and blue pixels can be adjusted electronically to bring the video into perfect
alignment, even if the laser beams are
not. This capability can also be used to
compensate for some types of chromatic
aberration if the PicoP is used as an
engine in a larger optical system.
Mapping from digital video coding to
laser drive is performed by the Adaptive
Laser Drive (ALD) system. The ALD is
a closed-loop system that uses optical
feedback from each laser to actively
compensate for changes in the laser
characteristics over temperature and
aging. This ensures optimum brightness,
color and grayscale performance. Unlike
other display systems, optical feedback
is incorporated to ensure optimum color
balance and grayscale.
REQUIREMENTS FOR PICO-PROJECTORS
In order to operate in a mobile format, pico-projectors will need to meet a
number of requirements related to the following dimensions.
Size: The height or thickness of the projector is its most
important characteristic; the technology must be able to
be embedded in thin handheld devices. Both height and
volume should be minimized. The initial products will have
projector engine sizes ranging in height from 7 to 14 mm
and in overall volume from 5 to 10 cc.
Brightness: The brighter, the better. Brightness is limited
by the available brightness of the light sources, either
lasers or LEDs, the optical efficiency of the projector
design, and by the need for low-power operation in order
to maximize battery life. Initial product offerings will be in
the range of 5-10 lumens.
Image size: In general, the shorter the distance it takes
for the projector to produce a large image, the better—at
least up to a point. A one-to-one distance/image-size ratio
(projection angle of 53 degrees) is probably a good target.
The first round of products on the market will have projection angles in the range of 30-45 degrees.
Focus-free operation: Focus-free operation is a very
desirable attribute in mobile applications. It is like “point
and shoot” in a camera. Unlike typical projectors used
in business settings, pico-projectors are designed for
mobile use. (In other words, the distance from the projector
to the image will likely change often.)
Resolution: Resolution can be expected to continue to
grow as product technology matures. The wide screen
format is generally desirable for viewing video content.
Initial product offerings will offer resolutions from QVGA
(320 x 240) to WVGA (848 x 480).
Color: Pico-projectors typically use either lasers or red,
green and blue LEDs for light sources. In both cases, the
result is large color gamuts that far exceed the usual color
range experience of TVs, monitors and conference-room-type projectors. White LEDs used with color filters yield a
reduced color gamut.
Contrast: The higher, the better. Just as brightness is a
measure of the absolute whiteness of pico-projectors,
contrast is the measure of their absolute darkness.
Contrast is the dynamic range of a display, making the
difference between washed-out images and crisp,
dramatic-looking images.
Battery life: A starting goal for mobile devices is that they
should last for the length of a complete movie. This puts
the lower limit at around 1. 5 hours.
